none Parasitation of the braconid A. manducator causes characteristic changes in the dynamics of pupation of C. vicina, depending on the age at which the host's instars are parasitized. If the parasitation was not successful, the host pupates simultaneously with the control or a little earlier, but when the parasitoid develops normally, formation of the host's puparia takes 8-9 days. Differences in the reaction on parasitation within one sample of the host are due to some differences in the instars age, because the result of the host-parasite interaction after a successful parasitation is strictly determined by the physiological age of the host at the moment of parasitation. Parasitation of the larvae short before pupation accelerates the latter, and the host develops to imago. When the parasitation occurs at an earlier stage, the host's metamorphosis stops, and in the case of incomplete oviposition or death of the parasitoid the larva of C. vicina transforms into an intermediate between larva and pupa form and dies soon after that. Pupation of the parasitized instars is possible only when the parasitoid survives and occurs about the time of its 1st molt. Abridgment of the host's metamorphosis probably is caused by distortion of the endocrine system of the latter by some factor, introduced by the parasitoid female at the moment of oviposition; the developing larva of the parasitoid stimulates pupation subsequently. Interaction of these effects enables A. manducator survival after the parasitation of C. vicina during the largest part of the larval stage.